Equivalent Circuit Components Research Articles

Frequency reconfigurable circular microstrip G-slotted antenna with DGS for various wireless applications

Frequency reconfigurable circular microstrip G-slotted antenna with DGS for various wireless applications

Linking Microstructure and Ionic/Electronic Conductivity in Composite Cathodes for Thiophosphate-Based All-Solid-State Lithium-Ion Batteries

Compared to conventional lithium-ion batteries (LIBs) with liquid electrolytes, ASSBs (all-solid-state batteries) have the potential to improve safety and achieve higher performance and energy density1. However, there are still many challenges to tackle in order to achieve ASSBs with sufficient cell performance, and one of them is to optimize the microstructure regarding its ionic and electronic conductivity. To achieve a high energy density, the fraction of AM must be as high as possible, and pores must be avoided. At the same time, an ionic conductive network of the SE has to be established; thus, both phases have to be distributed homogeneously with the composite cathode. On the other hand, the degradation of the solid electrolyte (SE) with cathode active material (CAM) and conductive additive (CA) has to be tackled with protective coatings that hinder the degradation but at the same time, keep the charge transport pathways open2,3. Therefore, the composite cathode microstructure (i.e., composition ratios CAM:SE:CA, particle characteristics, distribution of the phases) must be designed for different materials systems to ensure the sufficient percolation of ions and electrons for high performance4-9.In this study, we aim to understand the effect of the CAM fraction, morphology, and coating on the transport properties within the composite cathode. For this purpose, effective ionic and electronic conductivity of different cathode mixtures of Li6PS5Cl and NMC622 (coated, uncoated, single crystal, polycrystal) were analyzed and correlated with the microstructures. Moreover, a conductive matrix comprising Li6PS5Cl and C65 was introduced to the composite cathode system. Electronic and ionic conductivities were measured via impedance spectroscopy with ion- or electron-blocking electrodes in a symmetric cell configuration under constant pressure. To do so, a specially designed cell setup comprising a force sensor and a spring to adjust the pressure was used. The impedance spectra were fitted using T-type transmission line model (TLM) with equivalent circuit components with the RelaxIS 3 software package. Microstructural characterization was conducted on the powder mixtures and Ar- polished cross sections via scanning electron microscope using a transfer shuttle. We found the ionic and electronic transport limitations for the prepared composite cathode mixtures by varying the abovementioned parameters and optimized the CAM fraction accordingly. The results presented contribute to an improved understanding of the structure-property relationships and provide guidance on how to design a suitable microstructure.for improved cell performance. Acknowledgement The authors gratefully acknowledge the support of the German Federal Ministry of Education and Research within the program “FH‐Impuls” (Project SmartPro, Subproject SMART‐BAT, Grant no. 13FH4I07IA), Dr. Veit Steinbauer (Aalen University), Sebastian Puls and Dr. Nella Vargas-Barbosa (Helmholtz Institute Münster (IEK-12) - Forschungszentrum Jülich). References Janek, Jürgen, and Wolfgang G. Zeier.,Nature Energy 1.9 (2016): 1-4.Ma, Yuan et al., Advanced Functional Materials 32.23 (2022): 2111829.Sun, Shuo et al., Materials Futures 1.1 (2022): 012101.Noh, Sungwoo et al., Journal of Electroceramics 40 (2018): 293-299.Dewald, Georg F., et al., Batteries & Supercaps 4.1 (2021): 183-194.Ohno, Saneyuki, and Wolfgang G. Zeier., Accounts of Materials Research 2.10 (2021): 869-880.Bielefeld, Anja, Dominik A. Weber, and Jürgen Janek., ACS applied materials & interfaces 12.11 (2020): 12821-12833.Dixit, Marm et al., Solid State Batteries Volume 2: Materials and Advanced Devices. American Chemical Society, 2022. 113-132.Hendriks, Theodoor A. et al. ," Batteries & Supercaps (2023): e202200544

Time-Domain Modelling of Pulsed Photoconducting Sources—Part II: Characterization of an LT GaAs Bow-Tie Antenna

Drude’s description of the response of low-temperature gallium arsenide to optical pulse excitation is used to evaluate the components of a time-domain Norton equivalent circuit of a photoconductive antenna (PCA) source. The saturation of the terahertz (THz) radiated power occurring at large optical excitation levels was previously associated by the scientific community to radiation and charge screening of the bias. With the present circuit, we are able to model accurately the measured saturation as only due to the EM feedback from the antenna to the bias. The predicted THz radiated power is shown to match very accurately the measurements when the circuit is combined with an accurate description of the experimental conditions and the modeling of the THz quasi-optical (QO) channel.

A novel Dual Fractional-Order Extended Kalman Filter for the improved estimation of battery state of charge

Fractional-order models are gaining increasing relevance in battery modeling in light of the experimental measurements from Electrochemical Impedance Spectroscopy (EIS) tests, unequivocally indicating the presence of equivalent circuit components with an impedance of non-integer order. To attain their discrete state-space representation, the approach based on the Grünwald–Letnikov (GL) definition of the fractional derivative has been widely used, albeit its applicability beyond driving cycles remains open to discussion. In this article, we present a novel Dual Fractional-Order Extended Kalman Filter (DFOEKF) for the simultaneous estimation of State of Charge (SOC) and all fractional parameters, based on the multiple-RC approximation instead. We discuss the parameter identification of fractional-order elements on a NMC811/Si-Gr cell from both frequency and time-domain data, highlighting the importance of EIS measurements for the search of appropriate time-domain values. We validate the performance of this method experimentally at different operation stages, as well as its robustness to incorrect initializations, obtaining a SOC root-mean-square (RMS) error of 0.28% and a voltage RMS error of 15.2 mV in 20 complete charge–discharge cycles. The greatly accurate estimation results both within and outside the driving cycle stage make this method an interesting alternative for the fractional modeling of LIBs in online applications.

Impedantiometric behavior of solid biopolymer electrolyte elaborated from cassava starch synthesized in different pH

This paper approaches the study of pH’s effect on elaborate films of solid biopolymer electrolyte from cassava starch and its impedantiometric response. The films of solid biopolymer electrolyte were elaborated by thermochemical synthesis while varying the pH (2, 4, 5, 7, 9, 10, and 12). Starch was extracted from cassava tubers by a traditional method (disintegrated, washed, decanted, filtered, and dried). Solid biopolymer electrolyte films were processed by thermochemical synthesis by adding plasticizers (glycerol, glutaraldehyde, and polyethylene glycol) and lithium salt (lithium perchlorate). The impedance behavior was studied using the electrochemical impedance spectroscopy technique. The Nyquist and Bode’s diagrams registered presented a similar trend in all the films; therefore, they were described by the same equivalent circuit model. However, the equivalent circuit components presented different values in each case. The conductivity and capacitance showed a quadratic polynomial tendency in relation to the pH, obtaining the highest conductivity in the films elaborated at acidic pH and the highest capacitance in the films elaborated at basic pH. The degree of basicity or acids allowed conductivity to be modulated or capacitance of the solid biopolymer electrolyte as required. It could be concluded that the production pH has a marked effect on impedantiometric behavior of films of solid biopolymer electrolyte from cassava starch, which may be useful to modulate the electrochemical properties of this type of material in future Applications.

Constant phase element affected by ion transport in nanoporous electrodes

• A constant phase element (CPE) depends on the concentration of the electrolyte and ionic size at nanoporous electrodes. • Ion depletion in nanopores and the ion transport toward nanopores causes the non-ideality of the capacitance. • These findings are not observed at flat electrodes. A constant phase element (CPE) is an equivalent electrical circuit component that describes the behavior of a double layer formed at the electrode and electrolyte interface, which is a kind of imperfect capacitors. When the CPE concept is applied to model the behavior of the electrical double layer at nanoporous electrodes, the physical interpretation of the CPE becomes more complicated because of the morphological effect of the nanoporous electrode. Here we show that the CPE depends on the concentration of the electrolyte and ionic size at nanoporous electrodes. At low electrolyte concentration, the depletion of ions in the nanopore and the ion transport toward nanopores increase the dependence of capacitance on frequency. Moreover, larger ions have more restricted transport into the nanopore than smaller ions, leading to non-ideality of capacitance, which is significantly different from that of flat electrodes. The results suggest insight into the CPE at nanoporous electrodes.

Non-Destructive Impedance Monitoring of Bacterial Metabolic Activity towards Continuous Lead Biorecovery.

The adverse health effects of the presence of lead in wastewater streams are well documented, with conventional methods of lead recovery and removal suffering from disadvantages such as high energy costs, the production of toxic sludge, and low lead selectivity. Klebsiella pneumoniae and Paraclostridium bifermentans have been identified as potential lead-precipitating species for use in a lead recovery bioreactor. Electrical impedance spectroscopy (EIS) on a low-cost device is used to determine the potential for the probe-free and label-free monitoring of cell growth in a bioreactor containing these bacteria. A complex polynomial is fit for several reactive equivalent circuit components. A direct correlation is found between the extracted supercapacitance and the plated colony-forming unit count during the exponential growth phase, and a qualitative correlation is found between all elements of the measured reactance outside the exponential growth phase. Strong evidence is found that Pb(II) ions act as an anaerobic respiration co-substrate for both cells observed, with changes in plated count qualitatively mirrored in the Pb(II) concentration. Guidance is given on the implementation of EIS devices for continuous impedance monitoring.

Electrochemical impedance correlation analysis for the estimation of Li-ion battery state of charge, state of health and internal temperature

Electrochemical impedance spectroscopy (EIS) is an effective characterization tool for a multitude of battery states including state of charge (SoC), state of health (SoH) and internal temperature (IT). The intrinsic relationship between equivalent circuit elements and components of an impedance spectra (frequency, real, imaginary and phase) could be exploited to estimate the battery state at a given point of time without the need of continuous historical tracking information. Identification and analysis of battery state sensitive impedance variables is paramount for the development of any impedance-based battery management system (BMS). In this paper, correlation analysis between equivalent circuit elements and impedance spectra of multiple commercial Li-ion polymer batteries at varying SoC, SoH and IT levels was performed to identify and quantify the degree of dependence. Curve fitting techniques were used to fit the measured Impedance spectra on to an equivalent circuit model (ECM) to extract the circuit elements. Pearson's r correlation matrix was employed for quantifying the degree of correlation between each impedance variable and state parameter. Optimal impedance variables that demonstrated high dependence with SoC, SoH and IT are then proposed in this paper. Knowledge of this information is of high value to develop a direct impedance-based state estimation models for real time battery management systems.

Electrochemical Impedance Spectroscopy in the Characterisation and Application of Modified Electrodes for Electrochemical Sensors and Biosensors.

Electrochemical impedance spectroscopy is finding increasing use in electrochemical sensors and biosensors, both in their characterisation, including during successive phases of sensor construction, and in application as a quantitative determination technique. Much of the published work continues to make little use of all the information that can be furnished by full physical modelling and analysis of the impedance spectra, and thus does not throw more than a superficial light on the processes occurring. Analysis is often restricted to estimating values of charge transfer resistances without interpretation and ignoring other electrical equivalent circuit components. In this article, the important basics of electrochemical impedance for electrochemical sensors and biosensors are presented, focussing on the necessary electrical circuit elements. This is followed by examples of its use in characterisation and in electroanalytical applications, at the same time demonstrating how fuller use can be made of the information obtained from complete modelling and analysis of the data in the spectra, the values of the circuit components and their physical meaning. The future outlook for electrochemical impedance in the sensing field is discussed.

A new approach to investigate the ionic conductivity of NaCl and KCl solutions via impedance spectroscopy

Lima et al. [1] employed electrical impedance spectroscopy to analyze the electrical impedance behavior of dilute aqueous potassium chloride (KCl) and sodium chloride solutions in the frequency range of 10−1 Hz to 106 Hz (NaCl). The complex impedance Z* data from the solutions were modeled using an analogous electrical circuit that closely matched the experimental data. The electrical characteristics of the solutions were studied as a function of the cation types. The Debye model accurately describes the bulk effects of K+ and Na+ cations. However, it appeared that the analysis presented just the equivalent circuit components as a function of salt concentration. As a result, the current work used a simulation procedure to generate complex impedance (Z*) data from electrical parameters derived from the analogous circuit. To highlight the high-frequency relaxation processes occurring, extrapolation to a broader frequency range was performed. Furthermore, theoretical considerations were introduced in order to derive complex conductivity (σ*) from complex admittance (Y*). In the complex impedance (Z*) and admittance (Y*), there was a good correlation between all parameters derived from both processes. The key relaxation process characteristics, such as ionic strength, relaxation time, and conductivity values at low and high frequencies, were then retrieved. As a function of salt concentration, all of these parameters were evaluated and discussed.

Design of Squirrel-Cage Self-Excited 3-phase Induction Generator

Due to the wide utilization of a 3-phase, squirrel-cage, self-excitation generator in renewable energy and isolated areas application, the paper deals with detailed design procedure of this type of generator, in a sequence and systematic manner. The design steps are obtained and executed in a Matlab file of the computer program to suit the newly designed constructions and parameters of the generator. In the new construction, the generator can be operated in a stable and saturation region. Due to the similarity in the construction of induction motor and generator, the formulas used in the calculation of equivalent circuit components of an induction motor may be utilized to calculate the parameters of the induction generator. To obtain optimized induction generator parameters and construction dimensions an ant colony algorithm is used to optimize these construction dimensions and generator parameters. The main objective parameters used in this algorithm are the generator efficiency, the excitation-capacitance, winding temperature rise, and minimum generator size is for 5 HP, 400 V, 50 Hz, and star connection generator.

Modulation and Modeling of Three‐Dimensional Nanowire Assemblies Targeting Gas Sensors with High Response and Reliability

AbstractDespite improved sensitivity, simple downsizing of gas‐sensing components to randomly arranged nanostructures often faces challenges associated with unpredictable electrical conduction pathways. In the present study, controlled fabrication of three‐dimensional (3D) metal oxide nanowire networks is demonstrated that can greatly improve both signal stability and sensor response compared to random nanowire arrays. For example, the highest ever reported H2S gas response value, and a 5 times lower relative standard deviation of baseline resistance than that of random nanowires assemblies, are achieved with the ordered 3D nanowire network. Systematic engineering of 3D geometries and their modeling, utilizing equivalent circuit components, provide additional insights into the electrical conduction and gas‐sensing response of 3D assemblies, revealing the critical importance of wire‐to‐wire junction points and their arrangement. These findings suggest new design rules for both enhanced performance and reliability of chemical sensors, which may also be extended to other devices based on nanoscale building blocks.

The influence of the healing agent characteristics on the healing performance of epoxy coatings: Assessment of the repair process by EIS technique

The effects of the healing agents' molecular characteristics were studied on the self-healing performance of the epoxy coatings via corrosion evaluation techniques. Methylene diphenyl diisocyanate (kept constant) and different polyetheramine healing agents were encapsulated separately in poly(styrene-co-acrylonitrile) through the electrospray method and added to the epoxy matrix to prepare a polyurea-based dual capsule extrinsic healing system. Commercial grades of polyetheramine, Jeffamine D230, Jeffamine D400, and Jeffamine T403, were used to study the effects of molecular weight and functionality. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images revealed the formation of spherical shape with multicore morphology for the prepared polyetheramine containing microcapsules (MCs). Successful encapsulation was evaluated by Fourier transform infrared spectroscopy (FTIR), while the encapsulation yield was measured by thermogravimetric analysis (TGA). Electrochemical Impedance Spectroscopy (EIS) was employed to monitor the corrosion behaviour of a series of coated carbon steel samples through the evolution of the impedance spectra, and the numerical values of the related electrical equivalent circuit components (e.g., corrosion resistance), of the scratched coatings at different exposure times in a near-neutral 3.5 wt% NaCl solution. The results revealed the adverse effect on the corrosion protection ability by increasing the healing agent's molecular weight, while an increase of its functionality improved the final healing efficiency of the coating. According to the EIS results, the maximum healing efficiency was determined to be 85%, 72%, and 90% for Jeffamine D230, Jeffamine D400, and Jeffamine T403, respectively.

Electromagnetic effects of equatorially misaligned RF cavities

One of the most challenging problems in modern particle accelerator systems is the manufacture of RF cavities within the desired tolerance limits. In this study experimental and computational investigations to quantify the effects of transversal half-cell misalignments on the fundamental accelerator cavity parameters and beam dynamics are presented. Equivalent circuit components of an equatorially misaligned single-cell aluminum elliptical cavity are obtained from the measured data and are employed to calculate longitudinal impedance and modal wake function. Critical coupling and bead-pull measurements are performed at the TM010-like mode frequency, 2.45 GHz for the quality factor and shunt impedance of the high-β cavity. We report equivalent circuit analysis for higher-order modes and variations of the equivalent circuit components with respect to considered misalignment errors for the MICE experiment's muon cooling cavity. It is shown that using the equivalent circuit model decreases the computational load significantly for the wake field simulations of resonator cavities. Good agreement between simulations and measurements in terms of accelerating cavity parameters and impedances is illustrated.

Understanding the Impedance of CNOs-Graphene hybrid electrode through both experimental and simulated electrochemical impedance spectrum

Using a combination of experimental measurements and molecular dynamic (MD) simulations, we study the impedance of hybrid electrode composed of graphene and carbon nanometer onions (CNOs). On the experiment’s side, electrochemical measurements are conducted on the electrodde sample prepared from growing CNOs onto the graphitic plane. The general trend of impedance’s variations with frequencies is identified at different temperatures and ion concentration. Parameter fitting of equivalent circuit is accomplished with the assistance from machine learning technique using neural network. On the simulation’s side, electrode geometries including concave slit-pore and convex CNO-pore surfaces are modeled to investigate ion movements. Based on trajectories of ion dynamics, the physical origin of corresponding equivalent circuit component such as constant phase element is revealed. Regarding the geometry of electrode surface, the divide between planar and nonplanar part is observed in terms of charging level and charging time constant. Between the slit-pore and CNO-pore geometries, the differences in impedance spectrum is quantitatively characterized by solving the topology of and parameter of transmission line model of the equivalent circuit. In the branch of transmission line model, the resistance and capacitance are both larger for the space closer to the pore bottom or further from pore mouth.

Pairing electrochemical impedance spectroscopy with conducting membranes for the in situ characterization of membrane fouling

Protein fouling within a polymeric microfiltration membrane was characterized in situ and in real time with non-Faradaic electrochemical impedance spectroscopy (EIS). The polymeric membrane was prepared with a conductive gold coating, allowing the membrane surface to serve as a working electrode in a three-electrode EIS system. Utilizing the membrane surface as the working electrode allowed for differentiation between internal and external contributions to fouling. Protein fouling was able to be monitored qualitatively by observing changes in the resulting Bode and Nyquist plots and quantitatively by modeling the electrochemical system with equivalent circuit components comprised of resistive and capacitive elements. To our knowledge, this work represents the first attempt to deploy a conductive polymeric membrane as an active electrode in an EIS setup.

An Accurate Efficiency Calculation of Self-excited Induction Generator Including Effects of All Machine Parameters

In this paper an accurate method for efficiency calculation of self-excited induction generator (SEIG) at different operating conditions is proposed, considering the effect of stator and rotor iron core losses, stator and rotor circuits stray load losses, stator and rotor winding (copper) losses, mechanical losses, skin-effect losses, and skew-effect losses. The proposed procedure of efficiency calculation is based on the conventional machine tests such as no-load test, load test at variable supply voltage and temperature test without additional measurements. From these conventional tests, all the SEIG losses can be calculated accurately by their related formulas derived based on the SEIG equivalent circuit. The reduction of these losses causes an increase in the SEIG percentage efficiency, and this is a very important feature in electric energy saving by minimization of SEIG equivalent circuit components.

Unification of Internal Resistance Estimation Methods for Li-Ion Batteries Using Hysteresis-Free Equivalent Circuit Models

Internal resistance is one of the important parameters in the Li-Ion battery. This paper identifies it using two different methods: electrochemical impedance spectroscopy (EIS) and parameter estimation based on equivalent circuit model (ECM). Comparing internal resistance, the conventional parameter estimation method yields a different value than EIS. Therefore, a hysteresis-free parameter identification method based on ECM is proposed. The proposed technique separates hysteresis resistance from the effective resistance. It precisely estimated actual internal resistance, which matches the internal resistance obtained from EIS. In addition, state of charge, open circuit voltage, and different internal equivalent circuit components were identified. The least square method was used to identify the parameters based on ECM. A parameter extraction algorithm to interpret impedance spectrum obtained from the EIS. The algorithm is based on the properties of Nyquist plot, phasor algebra, and resonances. Experiments were conducted using a cellphone pouch battery and a cylindrical 18650 battery.

Study of Quartz Crystal Microbalance Behavior with Viscous Sensing Film

Introduction In odor sensing based upon QCM[1] sensing film is crucial for both sensor sensitivity and selectivity. The viscoelastic property of the sensing film greatly influences the response of the QCM sensor. The shear wave generated from QCM cannot penetrate deeply into the viscous sensing film. However, many appropriate sensing films with interesting properties are viscous. We would like to understand the behavior of the viscous sensing film although the behavior of the rigid sensing film is well understood. Method A QCM has an equivalent circuit derived from Mason equivalent circuit[2] as shown in fig. 1. Equations (1) and (2) indicate the acoustic impedance (Z3e) due to acoustic loading as a function of film thickness (h) film density (ρA1) and complex wave velocity (νA1). To extract QCM equivalent circuit component, we used a network analyzer to measure conductance from a QCM. Then, we apply the curve fitting technique to extract R1, L1, and C1 from the conductance curve[3]. This technique was used instead of a conventional motional admittance method (measure the frequency of maximum conductance). Because all the data were used for fitting the curve, this method is more robust and less susceptible to noise than conventional motional admittance method.The dip-coating technique was used for coating viscous film on QCM (9MHz, AT-cut). The QCMs were immersed into glycerol solution and then pulled-up with various speeds, which results in different film thicknesses. Results and Conclusions To replicate odor deposition into sensing film. We were using a small-size dispenser to deposit droplets of liquid onto QCM. Water droplet was shot onto the glycerol film as on a QCM. The preliminary result is shown in fig.2. The frequency was increased after each vapor exposure, whereas the resistance was decreased, we sometimes encountered increase in frequency due to vapor exposure at the highly viscous environment. We tried to understand its mechanism using the following analysis.The study was firstly done with liquid loading which represents viscous film. Only a singles side of QCM should be in contact with liquid. We calculated resonance frequency shift and resistance change as a function of water film thickness as is shown in fig. 3. Our calculation result based upon Mason equivalent circuit roughly agreed with both Kanazawa’s equation[4] and the experiment when the film thickness became large.To estimate film thickness and dynamic viscosity of the film, Mason equivalent circuit was used. The optimization was performed to obtain the dynamic viscosity and film thickness using the experimental data obtained from various film thicknesses. Fig. 4 shows the experimental data points at estimated film thickness and calculated curve. The simulation of Mason circuit shows good agreement with experimental data. Moreover, the simulation result also suggests that the frequency increase occurs due to liquid loading at a certain condition.We will perform the experiment on depositing tiny liquid droplets into sensing film before the conference.

Analysis, design and optimization of compact ultra-high sensitivity coreless induction coil sensors

For contactless inductive flow tomography we require a compact magnetic field measurement system with a dynamic range of 5 orders of magnitude in order to detect the amplitude and the phase of an alternating magnetic field of 1 mT strength with a precision better than 5 nT and a phase error no larger than 10−2 deg. In some applications a static magnetic field of about 300 mT is also present, resulting in a total dynamic range of 7 orders of magnitude.We present theoretical and experimental analyses of absolute and first order gradiometric induction coil sensors with sensitivities larger than 500 V/T · Hz) and diameters of 28 mm. From their equivalent circuits, we derive the associated complex-valued transfer functions and fit these to calibration measurements, thereby determining the value of the equivalent circuit components. This allows us to compensate their non-linear frequency-dependent amplitude and phase behaviour. Furthermore, we demonstrate the optimization of coils based on Brooks’ design of equal squares in the adaptation by Murgatroyd, which maximizes the inductance (and thereby most likely the sensitivity) of the coils. Finally, we design a new coil with a diameter of 74 mm and a sensitivity of 577 V/(T · Hz) with an analytically predicted equivalent magnetic field noise of around in the 1 Hz frequency range, which is then confirmed by measurements on the manufactured prototype.